[mapserver-users] mismatches tiling images produced by mapserver

[Norman Vine]

Brian Hill writes:
>>
>>That is, you ask for images that have a width of 0.30412 degrees and a
>>height of 0.22572 degrees (wid=0.30412&ht=0.22572) or a width/height
>>ratio of 1.34733, while your tiles are 821x771 pixels or a ratio of
>>1.06485.
>>
>Well, that could be.  There is indeed a redundant parameter here.  My 
>expectation was that one of them is just not used.  I should study the 
>sources and see which ratio takes precendence.  If this is 
>right, it is 
>exactly the kind of pointer I was hoping for.  Thanks.

Note that only the longitudinal 'map extent' is constant with respect to
arclength the latitudinal 'map height' vs arclength increases as one 
moves away from the equator in a mercator projection.

This complicates things a little but the tile sizes can be precomputed.

If you know that this data is always going to be 'displayed' in a mercator
projection another alternative is to store the data in the projected form.
This will simplify 'tile size problem' and may even display faster

Cheers

Norman